use of linq in asp.net projects?

That's right.  Linq to SQL. 

Really, Linq to SQL works reasonably well, but Microsoft seems to have moved on.  I wouldn't make something new with it, especially something that you want to maintain for several more years.

If you're making something new, I don't think you should use Linq.  Microsoft is no longer developing Linq.  The Linq team has been disbanded.

Microsoft is pushing Entity Framework now.  If you have a choice, I recommend you learn and use this newer Microsoft technology.

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